1. Field of the Invention
The present invention relates to a sealing device for a rotary machine such as compressors, gas expanders, etc.
2. Description of the Prior Art
A high speed rotary machine dealing with a high-pressure fluid involved a problem that an unstable vibration would be generated in a rotary body due to a vibration exciting force of the high-pressure fluid, resulting in deterioration of a sealing capability of the sealing device. Heretofore, as a counter-measure for precluding such type of unstable vibrations, proposals such that (1) a vibration attenuation effect was given to a bearing section provided in the proximity of the sealing device, and that (2) a rigidity for supporting a rotary body of a bearing section provided in the proximity of the sealing device was enhanced, were made.
At first, explaining the sealing device according to the proposal (1) above with reference to FIG. 6, reference numeral (101) designates a rotary body, numeral (102) designates an outer side of a rotary machine, numeral (103) designates an inner side of the rotary machine, numeral (130) designates a sealing device, numeral (110) designates a bearing device provided on the outer side of the rotary machine in the proximity of the sealing device (130). In this bearing device (102), reference numeral (111) designates a bearing metal, numeral (112) designates a bearing housing, numeral (113) designates a bearing housing lid, numeral (115) designates an oil film formed between the rotary body (101) and the bearing metal (111), numeral (122) designates seal rings having a rectangular cross-section, numeral (123) designates a support elastic member (123), numeral (125) designates a bearing stand, numeral (126) designates a bearing oil feed hole formed in the bearing stand (125), and numeral (126) designates a bearing oil feed hole formed in the bearing housing (112). In the above-mentioned sealing device (130), reference numeral (135) designates a casing (stationary member), numeral (133) designates a seal housing (stationary member), numeral (134) designates a seal flange (stationary member), numeral (131) designates a machine inside seal ring, numeral (132) designates a machine outside seal ring, numeral (136) designates a sealing fluid feed hole formed in the above-mentioned casing (135), numeral (137) designates a sealing fluid feed hole formed in the above-mentioned seal housing (133).
The bearing housing (112) and the bearing housing lid (113) are resiliently supported from the bearing stand (125) by means of the support elastic member (123), the bearing metal (111) is displaceably supported by the bearing housing (112) and the bearing housing lid (113), thereby the oil film (115) is formed between the bearing metal (111) and the rotary body (101), and between the bearing housing (112) and the bearing stand (125) is formed an oil film (121) which attenuates the vibration of the rotary body (101) through the "squeeze effect", which means the effect that the bearing housing (112) eccentrically deviates in a radial direction so that the oil existing between the bearing housing (112) and the bearing stand (125) is squeezed out from a narrowed gap portion to a broadened gap portion, hence, the vibration of the rotary body (101) is transmitted to the oil film (121) by the intermediary of the oil film (115).fwdarw.the bearing metal (111).fwdarw.the bearing housing (112), and thereby the vibration of the rotary body (101) can be attenuated. Also, at this moment, a sealing fluid is fed into an annular groove between the machine inside seal ring (131) and the machine outside seal ring (132) [that is, an annular groove formed between the seal housing (133) and the seal flange (134)] through the sealing fluid feed hole (136) and the sealing fluid feed hole (137), and thereby the gap space between the stationary members (133)-(135) and the rotary body (101) can be fluid-tightly sealed.
FIG. 7 shows another example of the sealing devices in the prior art, which is constructed similarly to the first example shown in FIG. 6 except that the seal rings (122) having a rectangular cross-section are replaced by O-rings.
Next, explaining the sealing device according the proposal (2) above with reference to FIG. 8, reference numeral (301) designates a rotary body, and a bearing device which rotatably supports the rotary body (301) is omitted in FIG. 8. Reference numeral (330) designates a sealing device, numeral (331) designates a machine inside seal ring, numeral (332) designates a machine outside seal ring, numeral (333) designates a seal housing (stationary member), numeral (334) designates a seal flange (stationary member), numeral (335) designates a casing (stationary member), numeral (351) designates a bearing pad, numeral (352) designates a setscrew, the bearing pad (351) is interposed between the machine inside seal ring (331) and the machine outside seal ring (332), the bearing pad (351) is fixedly secured to the machine outside seal ring (332) by means of the setscrew (352), and a dangerous speed of the rotary body (301) is raised by enhancing a support rigidity for the rotary body (301) by means of an oil film formed between the bearing pad (351) and the rotary body (301). It is to be noted that the machine outside seal ring (332) is necessitated to raise a rigidity against a support reaction force between the bearing pad (351) and the rotary body (301), and so, the machine outside seal ring (332) is adapted to be locked to the seal flange (334) by making use of a pressure difference between the front side and rear side of the machine outside seal ring (332).
In the sealing device for a rotary body in the prior art illustrated in FIG. 6 and described above, there exist the following problems:
(I) The bearing housing (112) and the bearing housing lid (113) are resiliently supported from the bearing stand (125) by the intermediary of the support elastic member (123), hence a vibration attenuating capability at the portion of the oil film (121) is increased, but a support rigidity for the rotary body (101) is lowered, and so a dangerous speed cannot be set somewhat high.
(II) Since the bearing housing (112) and the bearing housing rid (113) are resiliently supported from the bearing stand (125) by the intermediary of the support elastic member (123) as described above, centering upon assembly of the rotary body (101) is difficult, and moreover, as time elapses, deviation of centering would occur.
These problems equally exist in the sealing device in the prior art illustrated in FIG. 7.
Also, the sealing device for a rotary body in the prior art illustrated in FIG. 8 and described above involves the following problems:
(I) The bearing pad (351) is provided in the sealing device, hence a support rigidity for the rotary body (301) is enhanced, and a dangerous speed of the rotary body (301) can be set somewhat high, but a vibration attenuation effect cannot be expected so much from this.
(II) Presumption of practical load distribution is difficult due to floating up of the rotary body (301) upon acceleration and uncertainty of the timing of start of locking of the machine outside seal ring (332), and hence, a vibration characteristic of the entire sealing device including the bearing device cannot be precisely predicted.